MV DBMS platforms sometimes have built-in mechanisms for hot-backup and quick fail-over. Some rely on external software, perhaps products provided by OS vendors.
This is a place marker for information about hot-backup options available for each MV DBMS platform.
The High Availability Guide for Caché: http://docs.intersystems.com/cache20081/csp/docbook/DocBook.UI.Page.cls?KEY=GHA See topics for Shadow Journaling, System Failover Strategies, and ECP Failover.
A HotBackup license may be purchased for D3 *nix, not D3 NT. A "Using Hot Backup" PDF is available here: http://www.rainingdata.com/support/documentation/d3server.html
http://www.jbase.com/support/documentation.html See the jBASE Transaction Journaling PDF which includes a section on hot failover.
See the Resilience category: http://download.northgate-is.com/reality/V14%20Manuals/help.htm and topics Rapid Recovery, Shadow Database, FailSafe, and Disaster Recovery.
Maybe someone can pull the data from those links and create a new HotBackupU2 page?